In the past, industrial diamond and other hard materials such as cubic zirconium or carborundum have been used in various cutting operations where extreme hardness is required. Although such materials represent excellent surfaces for cutting or abrading, certain problems in durability have been encountered due primarily to thermal shock and cracking because of compressional forces.
Applicant has recognized that the parameters which control the durability of the cutting edges of ultra-hard crystalline materials can be modified and controlled by varying the mounting structures used to retain these crystalline materials in their cutting positions. Prior to applicant's invention, the cutting elements were held in place by one of two means. The first entailed the mere crimping of metal prongs about the crystalline surface. The second comprised the brazing of the crystalline materials in a stainless steel mounting.
Unfortunately, both standard prior art mounting techniques provided little to aid in the durability of the crystalline cutting surface. In each case, there was nothing to dissipate the tremendous shear and compressional forces which the cutting element is designed to encounter. Furthermore, the cutting element can suffer from thermal shock as neither mounting systems could be characterized as good thermal conductors. During grinding operations, the crystalline elements experience very high thermal conditions due to the frictional contact between the cutting surface and the material to be cut or ground.
When used as a drill bit, once the crystal was mounted, the orientation of the cutting surface would remain constant and fixed over the life of the drill bit itself. The present invention has also recognized the desirability for being able to design a mounting which would allow for a change in orientation so that as the cutting surface becomes worn in one plane, it can be rotated to display a second plane as the cutting surface.
Diamond, zirconium and carborundum (sapphire or ruby) cutting elements, for example, have also been used in making microtome knife blades. The blades, presenting an ultra-hard and ultra-sharp surface, have been used by the medical profession in performing biopsies where very thin layers of tissue must be cut accurately in the performance of pathological tests. Prior to the present invention, microtome blades were prepared by cutting a diamond or cubic zirconium stone along the major axis forming a knife blade. The stone was then mounted, resulting in misalignment of the blade axis to the microtome knife blade body. By employing the mounting of the present invention, alignment of the blade to the mounting is insured.
Similarly, these crystalline materials have been used to produce scribing tools, useful in scoring such things as semiconductor wafers. Prior art scribing tools have been made by sharpening crystalline bodies to a sharp point before mounting in an appropriate holder which resulted in misalignment of the scribe point to the holder body.